The area has a peak power need of 32MegaWatts but existing thermal plants can only supply 19MW, mass media minister Lakshman Yapa Abeywardena told reporters.
The power firm, Agrico runs a 12.5 MW plant and the CEB runs an old plant which can now deliver only 3MW of power, while Koolair provides the balance, an official said.
The CEB had originally installed an 8MW plant in 1958 but it had gone into dis-use following a protracted conflict in the area. It had been revived in 2006.
Jaffna has power cuts around 6.00 pm to 9.00 pm.
The plant built by a firm called Northern Power Limited will take over when the contracts for emergency power plants ends.
The minister says the agreement with Agrico will end in December. At the moment there are around 94,000 customers in Jaffna where the official pop